The present invention relates to a method of charging a hollow valve used in an internal combustion engine with metallic sodium, and an apparatus therefor.
Poppet valves used in an internal combustion engine, particularly for cars, are hollow to lighten and improve engine performance, and metallic sodium is sealed in a hollow valve stem to reduce thermal load.
As a method of charging a hollow poppet valve with metallic sodium and an apparatus therefor, in JP2012-136978A, a cavity of a workpiece, as a semi-finished product for a poppet valve, is open at a free end of a valve stem and is disposed at a working position in which the opening of the cavity is directed upward. A nozzle for feeding an inert gas and a metallic-sodium feeding tube are inserted into the opening. The metallic sodium is fed from the metallic-sodium feeding tube while the inert gas is fed from the nozzle. Hence, the cavity in the workpiece is charged with the metallic sodium without being oxidized with air in JP2012-136978A.
In JP2012-136978A in which an external diameter of the valve stem of the poppet valve and internal diameter of the cavity therein are large, it is possible to insert the inert-gas feeding nozzle into the cavity with the metallic-sodium feeding tube. When a diameter of the valve stem of the poppet valve and an internal diameter of the cavity therein are small, it is very difficult or impossible to insert the inert-gas feeding tube into the cavity with the metallic-sodium feeding tube.
In embodiment 2 in FIGS. 6 and 7 of JP2012-136978A, an inert gas 25 is introduced at an upstream side of the metallic sodium tank 16 via a three-way valve V31 and a regulating valve V41, and the metallic sodium is pressed into the cavity of the valve. However, the metallic-sodium feeding tubes and inert-gas feeding tubes become complicated and it is necessary to provide a lot of regulating valves thereby making the whole apparatus more complicated and larger. In actual operation, it is necessary to control a lot of regulating valves thereby making operation more complicated.